Potassium Metabisulfite — Hidden Processing Agent — Is It Vegan?

Vegan status: Vegan

Also known as: Potassium pyrosulphite, E224, KMBS, Campden tablet (contains KMBS or SMBS)

Source

Chemically synthesised from potassium hydroxide and sulphur dioxide. No animal products involved.

Used in

Wine production (antioxidant and antimicrobial), beer brewing (sterilising equipment, killing wild yeast), cider production, fruit juice preservation, winemaking.

Appears on label: No. Products containing sulphites above 10 ppm must declare 'contains sulphites' in EU and UK law. E224 may appear in the ingredient list of wines.

How to avoid

No need to avoid — KMBS is vegan. Sulphite sensitivity (distinct from vegan status) affects some people, particularly those with asthma.

Notes

Potassium metabisulfite is one of the most important preservatives in winemaking. Dissolved in water it forms sulphurous acid, which inhibits bacteria and oxidation. 'Campden tablets' used in home winemaking and brewing typically contain KMBS or SMBS. Low- and no-sulphite wines exist but may be less stable microbiologically.